An immersive content item is a content item that is made to be displayed around a user, so that the user has the feeling to be in the middle of the content. Immersive content may be a three-dimensional computer graphic imagery content (3D CGI), a volumetric video or a video mapped to a three-dimensional convex surface such as a sphere, a cube or a cylinder. Besides, a large two-dimension image of which the user could only see a part, by the means of a cropping for example, is also an immersive content; the user has to control the rendering device in order to see a not actually displayed part of the content.
Immersive content items are rendered by immersive rendering devices. For example, Head-Mounted Displays (HMD) are display devices, worn on the head or as part of a helmet, that have a small display optic in front of one eye (monocular HMD) or each eye (binocular HMD). They are advantageously adapted to consume immersive content items. In such a device, only a part of the video is displayed. The displayed part of the video content is updated according to the user head pose by the mean of an integrated Motion Unit Measurement (including a gyroscope) for instance and/or a pose estimating system using, for instance, cameras. A smartphone or a tablet may also render an immersive content. The displayed part is updated according to the orientation, and eventually according to the location, of the device.
The advent of such devices allows the user to watch a 4π steradians content by the means of movements, for instance head rotations. If such a feature may appear as a real improvement in terms of immersion in the content, as the user is watching at only a part of the content, he may not look at the direction he should look at a given moment. Indeed, as the user can gaze all around him, he may miss some important highlights of the narration because he is watching at another part of the content at the moment the narrative event happens.
According to the background art, it is known that forcing a virtual camera panning in order to make the user look toward the direction he has to look to, is a very efficient solution. However, it is well known that this solution has the drawback to make users sick and, as a consequence, to deteriorate the user's quality of experience. Pseudo-haptics methods degrading the content in the direction to avoid are known. They have the drawback to degrade the rendered images and so to modify the author's work and to alter the user's experience. Methods controlling a discrepancy between the aiming direction of the device controlled by the user's movement and the aiming direction of a virtual camera capturing the part of the scene to render are also an existing solution. They have the drawback of limiting the possible direction in which the user can look to.
There is a lack for a solution that friendly incites a user to look toward a direction (or a region) of interest without limiting his freedom of not following the incitement and without degrading his viewing experience.